<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>类选择器</title>
    <style>
        .red{ color: red;}
        .blue{ color: blue;}
        .green{ color: yellow;}
    </style>
</head>
<body>
    <div class="red">abbbs</div>
    <p class="blue">sdwdwd</p>
    <h1 class="green">sddqwfq</h1>
</body>
</html>